Glaucoma is a disease in which a disorder of the optic nerve which transmits visual information to the brain causes atrophy of the optic nerve to narrow the visual field. As the type of disease, for example, primary open-angle glaucoma (POAG), normal tension glaucoma, primary angle-closure glaucoma, developmental glaucoma, and secondary glaucoma are known. In addition, ocular hypertension, which is a state that the visual field is normal, but the intraocular pressure is chronically high, is one of the risk factors of glaucoma.
The onset mechanism of primary open-angle glaucoma (POAG) is considered to be that the trabecular meshwork which is an outlet of the aqueous humor is gradually clogged, whereby intraocular pressure (IOP) increases. The normal tension glaucoma is a disease in which although the intraocular pressure is in a normal range (10 to 21 mmHg), glaucoma is developed, and classified into primary open-angle glaucoma. The primary angle-closure glaucoma is a disease in which a corner angle becomes narrow to hinder the flow of the aqueous humor, thereby increasing intraocular pressure.
In the treatment of glaucoma, the first priority is considered to be decreasing intraocular pressure so that no further disturbance of the visual field progresses, and in order to decrease intraocular pressure, medication treatment, laser treatment, or surgical operation is performed. However, not all patients are satisfied with these existing treatments, and there is a need for a new therapeutic agent for glaucoma which contains effective component exhibiting a new mechanism of action or having a new structure unknown for the existing therapeutic agents.
Soluble guanylate cyclase (sGC) is an enzyme which produces cyclic guanosine monophosphate (cGMP) from guanosine triphosphate (GTP), and composed of a dimer of an α subunit and a β subunit. The β subunit is bound to heme, and usually iron coordinated to heme and a histidine residue which is the 105th amino acid interact with each other to take an inactivated structure. Nitrogen monoxide (NO) which is known as a main in vivo activation factor of sGC, interacts with heme iron present in the β subunit of sGC, and dissociates the interaction of the heme iron and the histidine residue of the β subunit, thereby performing transition to an activated structure. cGMP produced by activated sGC activates for example, the protein kinase or ion channel, and performs various roles such as relaxation of vascular smooth muscle inhibition of platelet activation, inhibition of cell growth, or olfactory neurotransmission (Non Patent Literatures 1 and 2).
sGC is also involved in the regulation of intraocular pressure, and Non Patent Literature 3 suggests that the sGC activator reduces a cell volume of the trabecular meshwork or the Schlemm's canal, which is the outlet of the aqueous humor, thereby promoting discharge of the aqueous humor, and representing intraocular pressure lowering. Thus, the sGC activator is expected as a therapeutic agent for glaucoma. Meanwhile, it is considered that in glaucoma, oxidative stress is enhanced, and also under the condition in which oxidative stress is enhanced, oxidation of heme iron or decomposition of heme is enhanced, and thus, as the therapeutic agent for glaucoma, heme-independent sGC activator is preferred (Non Patent Literatures 4 and 5). In addition, degrees of enhancement of oxidative stress are different for each patient, and become a factor of variation in a medicinal effect or side effects, and thus, variation of the activation effect due to the oxidation state of heme iron is preferably small.
Patent Literature 1 discloses that pyrazole carboxylic acid and imidazole carboxylic acid derivatives have a high effect on a monkey ocular hypertension model. However, though it is suggested that these derivatives are heme-independent, the degree of a change in the activation effect depending on the oxidation state of heme iron is not reviewed. In addition, Patent Literature 1 discloses that Cinaciguat which is a representative heme-independent sGC activator, has a low intraocular pressure lowering action.
Meanwhile, as a heme-independent sGC activator, Patent Literature 2 discloses a compound represented by General Formula A:
(for each symbol in the formula, see the publication), and Patent Literature 3 discloses a compound represented by General Formula B:

(for each symbol in the formula, see the publication). It is disclosed that the activity of these compounds is less dependent on the oxidation state of heme iron than that of Cinaciguat; however, the activity of lowering intraocular pressure is not evaluated in the document at all.